1. Field of Invention
The present invention relates to a semiconductor laser and a method of fabricating the same. More particularly, the present invention relates to a multiwavelength semiconductor laser array formed by a plurality of laser resonators and a method of fabricating the same.
2. Related Art
Recently, many research scholars have found that, compared with applications of semiconductor lasers such as bulk material without any quantum structure, quantum well, and quantum wire, the semiconductor laser having quantum dot as the active layer has an excellent laser property, and the quantum dot semiconductor laser is expected to have great potential in the application of the optoelectronic industry in the 21st century.
Conventionally, a quantum dot is mainly fabricated by means of molecular beam epitaxy (MBE) or metalorganic chemical vapor deposition (MOCVD) through a self-assembly method, such that the quantum dot is self-assembled on a surface of a specific substrate. Currently, the self-assembled quantum dot is applied to semiconductor amplifiers, ultrahigh brightness light emitting diodes, tunable wavelength semiconductor lasers, and multiwavelength semiconductor lasers, and so on.
In the application of the conventional multiwavelength semiconductor laser, the distributed feedback (DFB) laser and the distributed Bragg reflector (DBR) laser are mainly used as major semiconductor laser devices, and grating regions are disposed in/out of the devices and adjacent to the active layer, and thus, different emission wavelengths are selected based on different grating periods.
The multiwavelength semiconductor laser is usually generated in two ways. One way is to utilize a single semiconductor laser device to generate different laser wavelengths, for example, as disclosed in Japanese Publication Patent No. 2000340883, a super structure grating is employed to control the selective optical modal gain of the wavelength. The other way is to employ a laser array formed by multiple semiconductor laser devices, and each device of the array generates a single laser with a unique wavelength. For example, U.S. Pat. No. 6,600,169 and No.6,816,525 disclose an epitaxial growth mode relevant to quantum dots and quantum wires, and meanwhile, provide applications of the tunable wavelength laser and multiwavelength laser array directed to the gain spectrum of continuous bandwidths of the quantum dot, in which the quantum dot DFB laser and quantum dot DBR laser are used as major laser devices, and wavelength-dependent mirror loss is caused by different grating periods, such that laser arrays formed by different laser resonator units have threshold modal gain at different levels, thus generating lasers of multiple wavelengths.
However, the fabrication process of the above multiwavelength semiconductor laser is very complicated, and the subsequent epitaxial regrowth has a rather high cost.